Um I sit on both sides of the fence. On the one hand I feel they grossly disrespected you, abused their position, and were downright disgustingly terrible. But I also agree that you bear some responsibility here. I don't think it is the responsibility of your parents to make two meals every mealtime. The brunt of that is born by yourself. While unfortunate the situation is, assuming they are obligated to adhere to your non-medical dietary needs I think is rather out of line.

I did not catch your age. Perhaps if looking after your own needs in the household is impossible then it is time to find a place of your own.